Range-Subband Processing for Range Spectrum Aliasing Suppression in Squinted Multi-Channel Spaceborne SAR

Squinted multi-channel spaceborne synthetic aperture radar (SAR) offers wide-swath coverage and flexible observation geometry. However, imaging algorithms based on chirp scaling (CS) may broaden the range spectrum beyond the available sampling bandwidth, causing range spectrum aliasing and degrading the imaging quality of targets at the range edges of wide-swath scenes. To address this problem, this paper proposes a range-subband imaging method. First, a range spectrum broadening model is established to identify the main factors affecting spectral broadening. A subband division criterion is then derived to determine the minimum number of subbands required to avoid aliasing. Finally, a processing procedure comprising range-subband division, individual subband focusing, and coherent fusion is developed to recover the full-band range-focused signal. Point-target and distributed-target simulations verify that the proposed method suppresses range-spectrum aliasing and preserves full-band range resolution, while a broadside airborne experiment confirms that it introduces no appreciable image-quality degradation.